Thermal models of thrust faulting: Constraints from fluid-inclusion observations, Willard thrust sheet, Idaho-Utah-Wyoming thrust belt

Research Article| February 01, 1989 Thermal models of thrust faulting: Constraints from fluid-inclusion observations, Willard thrust sheet, Idaho-Utah-Wyoming thrust belt W. A. YONKEE; W. A. YONKEE 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 Search for other works by this author on: GSW Google Scholar W. T. PARRY; W. T. PARRY 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 Search for other works by this author on: GSW Google Scholar R. L. BRUHN; R. L. BRUHN 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 Search for other works by this author on: GSW Google Scholar P. H. CASHMAN P. H. CASHMAN 2Department of Geology, Mackay School of Mines, University of Nevada-Reno, Reno, Nevada 89557 Search for other works by this author on: GSW Google Scholar Author and Article Information W. A. YONKEE 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 W. T. PARRY 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 R. L. BRUHN 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 P. H. CASHMAN 2Department of Geology, Mackay School of Mines, University of Nevada-Reno, Reno, Nevada 89557 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1989) 101 (2): 304–313. https://doi.org/10.1130/0016-7606(1989)101<0304:TMOTFC>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation W. A. YONKEE, W. T. PARRY, R. L. BRUHN, P. H. CASHMAN; Thermal models of thrust faulting: Constraints from fluid-inclusion observations, Willard thrust sheet, Idaho-Utah-Wyoming thrust belt. GSA Bulletin 1989;; 101 (2): 304–313. doi: https://doi.org/10.1130/0016-7606(1989)101<0304:TMOTFC>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The thermal effects associated with emplacement of the Willard thrust sheet within the Idaho-Utah-Wyoming thrust belt have been numerically modeled. Fluid-inclusion studies and mineralogy, including illite crystallinity, narrowly limit choice of permissible thermal models. Permissible models have initial thermal gradients between about 30 °C/km and 35 °C/km and fluid pressures less than lithostatic pressure.Fluid inclusions were trapped in syntectonic veins within the basal part of the Willard thrust sheet and in cataclastically deformed basement within the footwall. Homogenization temperatures have a bimodal distribution in the Willard sheet with maxima at 180 °C and 260 °C and a unimodal distribution in the footwall with a maximum at 200 °C. These temperatures, along with fluid composition, determine fluid density and define isochores along which the fluids were trapped. Illite crystallinity and mineralogy record maximum temperatures in the range of 300 °C to 500 °C with somewhat lower maximum temperatures in the footwall.Thermal models for emplacement of the Willard sheet indicate that the hanging wall undergoes initial rapid cooling, but the footwall undergoes initial warming due to tectonic burial. Later both areas undergo approximately isothermal decompression as erosion proceeds. P-T paths for reasonable parameter values intersect the modal isochores and are consistent with mineralogy, as required for a permissible model. The thermal model provides a reasonable framework for understanding the thermal history of the Willard sheet. The models are sensitive to thrust-sheet thickness, initial heat flow, and thermal conductivity. The thermal models are relatively insensitive to erosion history for reasonable erosion rates and to redistribution of heat-producing elements for the low values typical of sedimentary rocks. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.